PT  - JOURNAL ARTICLE
AU  - Bessette, Erin E.
AU  - Fasco, Michael J.
AU  - Pentecost, Brian T.
AU  - Kaminsky, Laurence S.
TI  - MECHANISMS OF ARSENITE-MEDIATED DECREASES IN BENZO[<em>K</em>]FLUORANTHENE-INDUCED HUMAN CYTOCHROME P4501A1 LEVELS IN HEPG2 CELLS
AID  - 10.1124/dmd.104.002212
DP  - 2005 Mar 01
TA  - Drug Metabolism and Disposition
PG  - 312--320
VI  - 33
IP  - 3
4099  - http://dmd.aspetjournals.org/content/33/3/312.short
4100  - http://dmd.aspetjournals.org/content/33/3/312.full
SO  - Drug Metab Dispos2005 Mar 01; 33
AB  - Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are often environmental cocontaminants that could interact to alter PAH carcinogenicity. The heavy metal, arsenite, and the PAH, benzo[k]fluoranthene, were used as prototypes to investigate, in human HepG2 cells, mechanisms whereby the bioactivation of benzo[k]fluoranthene by human CYP1A1 could be diminished by arsenite-mediated decreases in CYP1A1 induction by benzo[k]fluoranthene. To determine whether arsenite down-regulates CYP1A1 transcription, quantitative real-time reverse transcriptase-polymerase chain reaction assays and luciferase reporter gene expression assays were used with HepG2 cells treated with benzo[k]fluoranthene and arsenite, separately and as a mixture. Benzo[k]fluoranthene (0.5 μM) and arsenite (5 μM) markedly decreased benzo[k]fluoranthene-mediated induction of CYP1A1 mRNA by 45%. Plasmids containing the CYP1A1 promoter region (pHu-1A1-FL) were induced 7.4-fold over vehicle by benzo[k]fluoranthene (0.5 μM), whereas arsenite (1, 2.5, or 5 μM) decreased reporter gene expression by 46%, 45%, and 61%, respectively. The plasmid, pHu-1A1-Δ100-FL, lacked xenobiotic response element (XRE) sites at –1061 and –981 and showed greater responsiveness relative to pHu-1A1-FL, by 1.7-fold. Benzo[k]fluoranthene (0.5 μM) and arsenite (1, 2.5, or 5 μM) decreased reporter gene expression by 0%, 27%, and 39%, respectively, relative to expression levels produced by benzo[k]fluoranthene alone. Arsenite is stable for at least 48 h in the HepG2 cell medium with respect to its ability to diminish CYP1A1 benzo[k]fluoranthene induction. Arsenite did not affect benzo[k]fluoranthene induction directly through XRE sites, nor did it affect the stability of CYP1A1 mRNA. Thus, arsenite affects the transcriptional regulation of the benzo[k]fluoranthene-mediated induction of CYP1A1 and could diminish PAH carcinogenicity by decreasing bioactivation by CYP1A1. The American Society for Pharmacology and Experimental Therapeutics